Food product extrusion apparatus and method

ABSTRACT

A tapered nozzle slightly compresses a mass of ground frozen meat to form a cohesive mass while retaining the spaghetti-like shape of the ground strands to aerate the cohesive mass. A positive displacement pump forces the meat through a grinding plate and then through the nozzle to a rotating involute knife to form patties of frozen ground meat in a continuous process.

This is a continuation-in-part application of application Ser. No.598,580 filed July 24, 1975, abandoned, which is a continuation ofapplication Ser. No. 454,159, filed Mar. 25, 1974, abandoned.

BACKGROUND OF THE INVENTION

In the processing of chopped meat patties in the prepackaged frozen foodindustry, the meat is prefrozen in bulk form. The meat is ground whilefrozen and a meat pattie is formed of the frozen chopped meat which isthen cooked prior to packaging and frozen in the cooked state.

The usual process in the industry for preparing the meat includeschipping or flaking the frozen bulk meat into a large mass of smallfrozen meat chips. These frozen chips are then processed through aconventional meat grinder. The meat is required to remain in the frozenstate during this processing. After grinding, the frozen meat is formedinto frozen chopped meat patties.

This forming process literally pounds the hard, frozen chopped meat intoa preformed meat pattie cavity. The cavity is then rotated or otherwisedisplaced to shear the packed meat within the cavity from the remainderof the extruded meat.

To thus pound the frozen meat into a compact tightly formed meat pattieproduces great stress on the machinery and causes frequent breakdownsthereof. Additionally, the shearing action involved in forming the meatpattie produces a waste material known in the art as "ooze." This "ooze"material is a material that is not fit for either animal or humanconsumption. Thus, this process produced thousands of patties within amatter of hours and hundreds of pounds of "ooze" material. Additionally,the pattie so formed has a finished cooked quality poorer than oneshould expect from the quality and grade of the raw product.

A further problem of the process is that the process needs to becontinually monitored to ensure that none of the frozen meat thaws andremains within the machinery which thawing could cause the meat tospoil.

SUMMARY OF THE INVENTION

In accordance with the present invention an extrusion nozzle is providedfor use with a solid food grinder of the type including a grinding platehaving a plurality of spaced apertures extending in a first direction.The plate including the apertures has a first area transverse the firstdirection. Solely the apertures have a second area transverse of thefirst direction which is less than the first area.

The nozzle comprises a housing having a hollow core tapered in a seconddirection from a wider inlet port to a narrow portion disposed withinthe housing. The narrow portion extends to a discharge port. The inletport has an area transverse the second direction of at least the samemagnitude as the first area. The narrow portion has an area transversethe second direction of about the same magnitude as the second area.Means are provided for coupling the inlet port adjacent the grindingplate.

A feature of the invention includes extruding means having an inlet portand an outlet port, the outlet port being coupled to the grinding plate.The extruding means includes a pressure pump including a pumping chamberand drive means closely fitted within the chamber to prevent cavitationof the food when driven by the drive means to the outlet port.

A further feature of the invention includes a rotating knife mountedadjacent the discharge port of the nozzle for portioning the extrudedproduct. The rotating knife has an involute cutting edge which edgeslidably transverses the discharge port when the knife rotates. Theknife includes a recess for receiving the mass of the extruded product.The recess of a given depth is disposed adjacent the cutting edge of theknife for receiving the end of the mass during the extrusion while theknife rotates to permit continuous extrusion during the portioningprocess.

A method of forming a cohesive mass of ground food having an adherentsurface comprises the steps of grinding the food into a plurality ofloose granular particles, and lightly compressing the particles togetherto form a cohesive-mass including air pockets disposed between theparticles within the mass.

IN THE DRAWINGS

FIG. 1 is an elevational view of a machine constructed in accordancewith an embodiment of the present invention,

FIG. 2 is an enlarged elevational cross sectional view of the extrusionportion of the machine of FIG. 1 including an extrusion nozzle,

FIG. 3 is an enlarged sectional view of a meat pattie formed by themachine of FIG. 1,

FIG. 4 is an elevational view of a knife used with the apparatus of FIG.1,

FIG. 5 is a cross sectional view of the knife of FIG. 5 aong lines 5--5,

FIG. 6a and 6b are sectional views of the extrusion nozzle and knifeassembly useful in explaining the operation of the apparatus of FIG. 1,and

FIG. 7 is a perspective sectional view of a meat pattie formed by theapparatus of FIG. 1.

DETAILED DESCRIPTION

In FIG. 1 extrusion apparatus 10 includes a positive displacement foodpump 12. Pump 12 is the type of machine usually used in the manufactureof sausages, bologna, salami and similar type of food product.

This produce is one wherein a highly compressed food product is forced,under pressure, into an elongated narrow casing to form a relativelyhard elongated tubular mass of compressed food.

Such a machine is not ordinarily used in a food processing art to grindmeat or the like. The grinding process is confined to a lesssophisticated and cheaper apparatus using a well known auger andapertured grinding plate. However, in accordance with one feature of thepresent invention, a pump machine of the type described above isutilized to produce ground or chopped meat. One suitable pump machine ismodel Vemag 3000S manufactured for the Robert Reiser Co., Inc. ofBoston, Mass.

Secured to machine or pump 12 is a hopper 14 which supplies by gravitychipped frozen meat or bulk thawed meat, as the case may be, to thepumping cavities 16 of machine 12. The pump of machine 12 includes inone form, twin pump screws 42 which are disposed within cavities 16which together form an elongated cross section. The discharge ports 18of pumping cavities 16 are coupled to an adapter 20. Adapter 20 convertsthe generally elongated pump cavities 16 to a generally circular oroblonged shaped cavity at the discharge end 22 of adapter 20. Secured toeach of screws 42 in direct drive therewith are a pair of conventionalcutters 23a and 23b. Cutters 23a and 23b each rotate in response to therotation of the corresponding screw 42 for cutting up the meat prior tofurther extrusion in the direction 58. Sealingly secured to adapter 20is a planar conventional grind plate 24 having a plurality of apertures26 disposed therein. Sealingly connected to the other side of grindplate 24 opposite the discharge end 22 is nozzle 28 constructed inaccordance with the present invention to be described in connection withFIG. 2. Nozzle 28 is connected to pattie forming assembly 29 mounted intable 30.

Assembly 29 includes a knife drive motor 32 which drives a rotatingknife 34 (FIG. 2) by way of gear box 36. Patties are formed by assembly29 by slicing the patties from the extrusion mass flowing from nozzle28. Disposed directly beneath nozzle 28 is an endless conveyor beltassembly 38 which carries away patties 40 formed by the assembly 29.Machine 12 is a positive displacement pump having a pair of twin screws42 closely fitted within the cavity 16 so as to provide a positivepressure on food particles disposed within the cavity 16. In effect,screws 42 act as pump gears rather than a mere conveying means such as aconventional auger. This positive pressure prevents what is known in theart as cavitation.

Generally in the meat grinding art an auger or screw is placed within anoversized cavity and the screw is rotated to force the meat productagainst an apertured plate at one end of the axially disposed screw. Bypacking the meat product into the auger, the screw action of the augerforces the meat past a revolving cutter against the aperture plate andthus forces the meat through the plate apertures. However, due to theloose tolerance existing between this auger and its correspondingcavity, the density of the meat forced against the aperture plate is notalways uniform. Further, variations of back pressure in accordance withthe amount of meat supplied to the auger may cause some of the meat tobe displaced between the screw or auger blades and the auger cavity.When the meat remains stationary, as the auger rotates, it will tend tothaw and therefore will be subject to spoilage. The stationarydisposition of the meat within the auger cavity as the auger rotates isknown in this art as cavitation. As a result, the meat grinding processportion has been separate from the pattie forming process in the frozenfood industry. That is, frozen meat is ground and then the ground frozenmeat is separately supplied to the pattie forming apparatus.

However, as provided in accordance with a feature of the presentinvention, the use of a positive displacement pump prevents theoccurrence of cavitation and permits the use of the grinding step aspart of a continuous process in the manufacture of meat patties. Thisprovides a marked improvement in the efficiency of the pattie formingprocess.

The pump 12 is disposed with the screws 42 oriented in a verticaldirection with respect to the earth such that patties 40, when formed,drop by gravity to the conveyor belt 38. Suitable mounting means (notshown) are provided for mounting pump 12 in this orientation.

In FIG. 2 there is illustrated extrusion nozzle 28 constructed inaccordance with the present invention. Nozzle 28 has a cavity 52 definedby an inlet port 44 which tapers to a narrower conduit portion 46disposed within the nozzle 28. Narrow portion 46 has a uniform crosssectional area which continues to the discharge port 48 of nozzle 28 inthe extrusion direction 58. The alignment of cavity 50 of adapter 20 andcavity 52 of nozzle 28 is preferably in the same direction 58. Suitablefastening means (not shown) connect nozzle 28 sealingly to aperturegrind plate 24 and, in turn, sealingly connect grind plate 24 to adapter20 and adapter 20 to machine 12 at cavities 16. As known to thoseskilled in the meat grinding art, plate 24 is commercially available inat least thicknesses of one-quarter and one-half inches in accordancewith the number of apertures in the respective plate. For example, aone-quarter inch plate may have approximately 50-100 apertures while aone-half inch plate may have 500-900 apertures. The size of the apertureplate selected, of course, depends on whether miniature hamburgers inthe order of about 1 or 2 square inches in transverse cross-section ormeat loaf in the order of about 20 square inches in transversecross-section are desired.

It will be further appreciated that the relatively thin aperture plate24 minimizes mechanical rendering of the meat. In rendering, the fat inthe meat migrates to the aperture walls forming a thick film inside thewalls. Such rendering tends to reduce the otherwise natural adhesivenessof the raw meat at the surface of the strands.

Apertures 26 in plate 24 are disposed in a circular array having adiameter D. The transverse area of the circular plate including allapertures 26 within diameter D has a known area A. This area includesthe cross sectional area A_(a) of the apertures 26 and the crosssectional area of the intermediate portions 54 of plate 24 surroundingand defining apertures 26. Necessarily the total transverse area A ofthe intermediate portions 54 and apertures 26 is larger than the totalcombined transverse area A_(a) of apertures 26 alone.

Inlet port 44 of nozzle 28 is provided with a transverse cross sectionalarea that is at least as great as the combined transverse crosssectional area of apertures 26 and the intermediate portions 54comprising area A. The inlet port 44 tapers uniformly to the narrowertransverse cross sectional area at portion 46 to provide laminar flow ofthe ground meat. The cross sectional area A_(d) of narrower portion 46is about the same magnitude as the transverse cross sectional area A_(a)of apertures 26 within area A. The value of portion 46 area A_(d) ispreferably about 5% greater than the aperture area A_(a) when processingmeat.

When the strands 59 (FIG. 3) of chopped meat flowing through cavity 52reach narrower nozzle portion 46, the strands remain substantiallyparallel to each other and contiguous. The area A_(d) of portion 46lightly compresses or squeezes the strands 59 together in a radial orlateral inward direction transverse the direction 58 forming a cohesivemass of all of the naturally adherent strands 59 within portion 46.However, the mass is not so tightly compressed by the tapering action asto remove all of the air pockets 60 (FIG. 3) disposed within the massintermediate the various strands or destroy the strandlike configurationof the raw meat. This action is achieved by the relationship of areaA_(d) to area A_(a) and the extruding forces in direction 58. Theseforces are not critical and can have any value sufficient to force themeat through apertures 26. Thus these forces may be produced by a handauger, as well as a pump such as pump 12.

FIG. 3 is a partial enlarged sectional view of some of the strands 59 ofchopped meat disposed within narrow portion 46 of nozzle 28. Each of thestrands 59 is contiguous with the next adjacent strands, however, someair space 60 remains between the strands. Thus, while the stands havebeen compressed or directed together sufficiently to form a singlecohesive mass and some deformation occurs, each of the strands are stillreadily identifiable in cross section in the raw state. It is thusapparent that plain, natural red meats of the type, for example,including steer, calf, lamb, pork and the like can be formed into anaturally adherent aerated mass. It should be further apparent that thestrands are separately identifiable in the raw and cooked states withoutfibrous additives.

It will occur to those skilled in the meat processing art that suchadditives as grain, onions, eggs, and seasoning, individually or in anycombination may be used to enhance the flavor of the product.

The extended length of narrow portion 46 disposed between taperedportion 56 and the discharge port 48 may be of any suitable mangitude asknown in the extrusion art to provide an elongated mass of chopped meathaving a substantially uniform cross section when discharged from nozzle28. Nozzle 28 may be made of any suitable material but is preferablymade of stainless steel.

The discharge port 48 of nozzle 28 is secured in a suitable manner toknife wear plate 62. Wear plate 62 is a planar plate of hardened metalwhich serves as a guide and coacting cutting surface for rotating knife34. Wear plate 62 has a hole 64 of about the same transverse sectionarea as area A_(d) of portion 46 and is disposed adjacent the dischargeport 48 to form a continuous conduit therewith. Wear plate 62 is securedto table 30 (FIG. 1) in a suitable manner (not shown).

All the elements including machine 12, adapter 20, plate 24, nozzle 28and wear plate 62 are tightly secured together to prevent oozing of anyof the meat product at the connected joints therebetween. Disposedadjacent wear plate 62 is rotating involute knife 34. Knife 34 issecured to gear box 36 at gear box output drive 66. A spacer ring 68 issecured around the periphery of circular wear plate 62 to form a kniferotating cavity 70. Knife cover plate 72 is secured to spacer ring 68 toenclose cavity 70. Knife 34 is disposed with the direction of rotationof the blade thereof normal to the extrusion direction 58. Cover plate72 has a hole 74 which is aligned with hole 64 and cavity 52 and forms acontinuous conduit therewith. Secured to a side of plate 72 oppositecavity 70 is safety housing 76 to protect personnel from being injuredby rotating blade 34. Housing 76 is a hollow conduit fastened to coverplate 72. The conduit of housing 76 is also axially aligned with theextrusion direction 58. Knife drive 66 rotates about drive axis 78.

In describing the knife 34, reference is made to FIGS. 4 and 5, whereinknife 34 includes a mounting plate 84 and a blade 86 depending from themounting plate. Blade 86 has a cutting edge 90 formed along an involutecurve intersecting the axis of rotation 92 of knife 34. Cutting edge 90is preferably provided as an inside edge of the blade. One face 94 ofknife 34 tapers toward a second face 96 terminating in cutting edge 90.Face 96 is disposed normal to the axis of rotation 92 of knife 34. Face94 terminates at blade surface 98 which extends to the non-cuttingperipheral edge 100 of the blade 86.

Edge 100 commencing at blade end 102 follows a general convex curve tomounting plate 84. Blade 86 is machete-like in shape. Recess 104 isformed in blade 86 on the side thereof opposite blade surface 98. Recess104 extends from face 96 to edge 100. Recess 104 has a predetermineddepth d. Depth d is determined in conjunction with the angular rate ofrotation of knife 34 and the feed rate of the cohesive mass flowingthrough the nozzle discharge port 48 in a manner to be explained. Thesize of the blade is determined in a conventional manner with respect tothe size of the cross sectional area of discharge port 48 of nozzle 28such that the cutting edge 90 extends transversely across discharge port48 as knife 34 is rotated. Face 96 of blade 86 is disposed contiguouswith cutting surface 106 on wear plate 62 as is known in the cuttingtool art, (see FIG. 2). In FIG. 2, recess 104 is disposed facingdischarge port 48. Recess 104 serves to receive the extruded mass oflightly compressed extruded meat after face 96 passes through the meat.This operation will be explained in connection with FIGS. 6a and 6b.

In operation, screws 42 force with a positive pressure chipped frozenmeat into cavity 50 of adaptor 20. The inside walls 106 of cavity 50 aretapered from discharge port 18 of pump 12 to narrow discharge end 22 ina manner to provide a minimum of turbulence in the flow of the chippedmeat to prevent cavitation thereof within cavity 50. This is importantfor the reason that should cavitation, that is stagnation of a portionof the meat, take place within cavity 50, that portion of meat will thawand spoil. The meat under pressure is forced through conventionalcutters 23a and 23b and thence through plate 24 forming a plurality ofspaghetti-like strands 59 (FIG. 3) of meat. Cutters 23a and 23b, incutting up the mass of meat just prior to entering apertures 26, preventthe clogging of apertures 26 in a conventional manner. The cut meatentering apertures 26 comprises a plurality of naturally adherentparticles. The particles when forced through the apertures 26 are formedinto the strand configuration.

The strands 59 are then directed together in laminar flow in thedirection 58 by the tapered narrowing configuration of tapered portion56 of nozzle 28. The spaghetti-like strands continue to flow throughcavity 52 as a cohesive extruded mass having a plurality of air pockets60 (FIG. 3) between adjacent strands within the mass. Nozzle portion 46aligns the strands substantially parallel. The substantially parallelnature of the strands provides an elongated granular structure to thecohesive mass. The mass continues to flow toward knife 34. In themeantime knife 34 is rotating at a predetermined rate which issynchronized with the flow rate of the mass of extruded meat. Thesynchronism is such that the mass continues to flow at all times withoutbacking up against blade 86.

In FIGS. 6a and 6b there is illustrated a severed meat pattie 110.Severed meat pattie 110 has an outer configuration determined largely bythe shape of the extrusion nozzle 28 discharge port 48. Knife 34 isshown in a position where it has fully severed the meat pattie 110 withthe blade 86 still blocking the passage way to the discharge port 48.Unless otherwise provided for, the meat would tend to be stalled at thedischarge port until the blade 86 is rotated beyond the path of theextruded mass flow. This would cause an undesirable backing up of themass, a non-uniform meat pattie and would unduly compress the meateliminating the air pockets 60 (FIG. 3).

In the prior art machines, the feed of the extruded mass is usually madeintermittent, that is the feeding is stopped for short periods of time,to prevent the undesirable backing up of the material during the pattieforming process. However, in accordance with the present invention themanufacture of the cohesive extruded mass is continuous by providingrecess 104 in knife 34. By providing recess 104 directly behind face 96of the rotating blade, the meat that is extruded continues to flowtoward the rotating knife and is received by recess 104. This receivedportion 112 is the leading edge of the extruded mass which forms part ofthe next subsequent formed meat pattie. The depth d of the recess (FIG.5), the rate of rotation of the knife, the size of the knife and thefeed rate of the cohesive mass of the meat are all predetermined in aconventional manner by well known principles.

It will be appreciated that at high mass production rates, for example200 patties per minute, knife 34 rotates at 200 rpm and processesapproximately 600 ounces of meat per minute through pump 12. At theserates, even the relatively small amount of meat that would be compressedagainst the blade 86 of knife 34, should recess 104 not be provided,would produce a relatively large backup of extruded meat within thenozzle 28 in a short period of time.

The provision of air pockets 60 and the substantially elongated granularstructure of the meat pattie, as illustrated in FIG. 7, provides a meatpattie that is extremely tender and tasty. The juices, when cooked, tendto remain within the air pockets disposed within the meat pattie and theloose formation of the various spaghetti strands of extruded meat tendto remain tender as compared with meat patties formed by pounding andotherwise tight packing.

By the use of knife 34 as compared to the shearing action provided inprior art devices, virtually no ooze is produced. Knife 34 issufficiently sharp to provide a clean cut of the pattie producing almostno waste. The ground meat, when frozen, is not an easy material to cut.As a result, the involute curve provided edge 90 of knife 34 (FIG. 4)provides a sliding action with respect to the meat pattie during thecutting process. This sliding action produces a cleaner cut thanotherwise possible.

It should be understood that while the involute knife edge 90 isdisposed on the interior curve of blade plate 86, an involute cuttingedge may, in the alternative, be provided knife 34 at the exteriorperipheral edge 100.

As the meat patties are severed, they fall by gravity onto conveyor 80(FIG. 2) and are conveyed in the usual manner. By using the meat pump12, adapter 20 in conjunction with grinding plate 24 and nozzle 28 andknife 34, a continuous pattie forming process is provided for what hasbeen heretofore a difficult process to automate in the fast frozen foodindustry. In particular, waste has been substantially eliminated,cavitation and spoilage within the product has been overcome and atendered, juicier product for a given quality of raw food is provided atless cost than heretofore possible. It should be appreciated that whilea food pump 12 has been illustrated in the embodiment of the presentinvention, conventional grinding plates and augers may also be used withthe nozzle 28 where a discontinuous process is acceptable.

There follows examples of the use of the invention in making varioustypes of meat patties.

                  EXAMPLE I                                                       ______________________________________                                        Meat         natural raw frozen chipped steer beef,                                        no additives, less than 30% fat.                                 Aperture plate 24                                                                          thickness - 1/4 inch                                                          number of apertures - about 90                                                diameter of apertures - 0.156 inches                             Nozzle 28    a) inlet opening - 23/4 inches                                                b) axial length (direction 58) -                                                about 13/8 inches                                                           c) exit opening - transverse diameter                                           (round) - 11/2 inches                                          Power Source Hobart Laboratory Grinder                                                     1725 RPM, 1/4 H.P. motor                                                      Conventional screw type auger                                    Pattie Thickness                                                                           3/8 to 1 inch                                                    ______________________________________                                    

                  EXAMPLE II                                                      ______________________________________                                        Meat         natural raw frozen chipped steer                                              beef, no additives, less than 30% fat                            Aperture plate 24                                                                          thickness - 1/4 inch                                                          number of apertures - about 60                                                diameter of apertures - 0.156 inches                             Nozzle 28    a) inlet opening - 23/4  inches                                                 transverse diameter (round)                                                 b) axial length (direction 58) -                                                about 13/8  inches                                                          c) exit opening - 1.1 × 1.1 inches                                        (square)                                                       Power Source Hobart Laboratory Grinder                                                     1727 RPM, 1/4 H.P. motor                                                      Conventional screw type auger                                    Pattie Thickness                                                                           3/8 to 1 inch                                                    ______________________________________                                    

                  EXAMPLE III                                                     ______________________________________                                        Meat         natural raw frozen chipped steer                                              beef and veal, no additives, less                                             than 30% fat, separately processed                                            to form beef and veal patties.                                   Aperture plate 24                                                                          thickness - 1/4 inch                                                          number of apertures - about 596                                               diameter of apertures - 0.187 inches                             Nozzle 28    a) inlet opening - 5 inches                                                   b) axial length (direction 58) -                                                about 5 inches                                                              c) exit opening - about 45/8  ×                                           3 9/16 inches (rectangular)                                                 d) axial length of portion 44 -                                                 about 2 inches                                                 Power Source 15 H.P., variable speed pump                                     Pattie Thickness                                                                           3/8 inch to 1 inch                                               ______________________________________                                    

                  EXAMPLE IV                                                      ______________________________________                                        Meat         raw frozen chipped steer beef with                                            bread crumbs, dried onions, dried                                             eggs and salt added.                                             Aperture plate 24                                                                          thickness - 1/2 inch                                                          number of apertures - about 815                                               diameter of apertures - 0.187 inches                             Nozzle 28    a) inlet opening 73/8  inches                                                   transverse diameter (round)                                                 b) axial length (direction 58) -                                                about 3 inches                                                              c) exit opening - 4 × 55/8  inches                                      d) axial length portion 44 -                                                    about 2 inches                                                 Power Source 60 H.P., variable speed -                                                     conventional screw type auger                                    Pattie Thickness                                                                           3/8 inch to meat loaf proportions                                             (various lengths).                                               ______________________________________                                    

What is claimed is:
 1. A method of forming a cohesive mass of rawchopped meat having a naturally adherent surface comprising the stepsof,grinding the meat into a plurality of strands of circular crosssection, each strand having a naturally adherent surface, flowing thestrands-together wherein said flowing includes directing said strandsradially inwardly, to form a naturally cohesive mass wherein all meat inthe mass is raw, while retaining the circular cross section of theindividual strands including a plurality of air pockets formed by thegeometry of said strands disposed between adjacent ones of said strandswithin said mass and periodically severing said cohesive meat mass. 2.The method of claim 1 wherein said flowing step including the steps ofdirecting said strands together transverse the elongated axis of saidstrands, and aligning said said elongated strands substantiallyparallel.
 3. The method of claim 2 wherein said strands each have agiven transverse cross sectional area, said directing step directingsaid strands together an amount wherein the total transverse crosssectional area of said directed cohesive mass is greater than the totalcombined cross sectional area of all said elongated strands.
 4. Themethod of claim 3 including the step of severing said cohesive masstransverse the elongated axis of said directed strands.
 5. The method ofclaim 1 wherein said grinding step includes the step of pumping saidmeat through an apertured plate to form a plurality of elongated strandsof said meat, andsaid flowing step includes directing radially inwardlysaid strands transverse the elongated axis of said strands so that thetransverse cross sectional area of said directed strands is greater thanthe combined cross sectional area of solely said plurality of strands.6. The method of claim 1 wherein said meat is frozen prior to saidgrinding.
 7. The method of claim 1 further including the step ofcontinuously forming said cohesive mass into a plurality of patties. 8.A method of making frozen chopped raw meat patties comprising the stepsof:extruding frozen raw meat including forming the frozen meat into aplurality of strands of circular cross section, continuously passingsaid strands through an inwardly tapered conduit at a given velocity toform a cylindrical mass of strands wherein all meat in the mass is rawand which strands adhere to one another and yet which retain theircircular cross section whereby said mass by virtue of the geometry ofthe strands includes a plurality of air pockets which extend in thedirection of the axis of said cylindrical mass and which are disposedbetween adjacent surfaces of said strands, and periodically severingfrom the end portion of said cylindrical mass a meat pattie.
 9. Themethod of claim 8 wherein said extruding process includes the step ofpumping said meat through an apertured grinding plate.
 10. The method ofclaim 8 wherein said extruding process includes the step of forming theelongated strands into a cohesive mass having a plurality of air pocketsdisposed intermediate said strands.
 11. A method of making meat pattiesemploying a plate having circularly shaped apertures therein, theapertures having a total area of A_(a), comprising the steps of:forcingnaturally sticky raw meat through said apertured plate to form aplurality of discrete strands of meat; as they emerge from the plate,passing the strands through a funnel shaped passage having an exitopening of area A_(d) which is approximately equal to A_(a), whereby thestrands, as they pass through said exit opening are gently forced intocontact with one another and adhere to one another while substantiallyretaining their circular cross section so that pockets of air remainpresent between each strand and the strands in contact with andsurrounding that strand; due to the geometry of said strands wherein allthe meat in the strands is raw, and severing from the mass of meatpassing from the exit opening of said passage successive patties bycutting the mass in a direction transverse to the central axis of thefunnel shaped passage.
 12. A method of forming a cohesive mass of rawchopped meat from the kind of meat which when ground is sticky,comprising the steps of:forming the meat into a plurality of strands ofcircular cross section which because of the sticky property of the meatcomprises strands having sticky outer surfaces; flowing the strandstogether to form said cohesive mass, wherein said flowing includesdirecting said strands radially inwardly, so that each strands abuts atits outer surface other strands but in the process retains its circularcross section, said strands adhering to one another where they come incontact with one another, but as they remain of circular cross section,air pockets remain between adjacent strands and such that all meat inthe strands is raw, and periodically severing said cohesive mass.